Dial test indicator



y 1956 E. J. WITCHGER 2,755,557

DIAL TEST INDICATOR Filed DEC. 9, 1952 IN VEN TOR.

Wa iMQ ILM A TTORNEYS DIAL rssr INDICATOR Eugene Witchger, Saginaw,Mich, assignor to The Lnfitin Rule ompany, Saginaw, Mich.

Application December 9, 1952, Serial No. 324,913

3 Claims. (Cl. 33-172) This invention relates to inside attachments fordial test indicators for lining up shafts, checking holes, slots and theunderside-s of surfaces and the like, and more particularly to a meansfor confining or limiting the movement of the attachment arm.

in some previous devices of the type herein described, the attachmentarm has been swivelly mounted in the manner illustrated and described inFatcnt No. 2,345,845, to permit all of the parts, except the extendingend thereof, to be totally enclosed and protected against clogging andabrasive machinings, dirt, grit, and the like. While these prior artdevices were very satisfactory from this standpoint, and could beeconomically manufactured and assembled, it was found, in actualpractice, that they were not as accurate as desired. if the arm ispermitted to turn in its socket or revolve, the readings will often beinaccurate since the indicating arm may, in some instances, merely turnin its socket and avoid the untrue surface without imparting a movementto the plunger. Further, if the ball joints of the attachment orindicating arm joint and the sockets in which they are mounted in adevice in which the arm is per .iittsd to freely revolve are notabsolutely true, some error occurs.

Other devices have employed a pin through the attachment joint torestrict the movement of the arm to a definite plane, but since it isdesirable to provide a removable attachment arm threaded in the casing,it will be obvious that the arm cannot, without great difficulty andadjustment, be threaded in-so that the pin will always be at rightangles to the plane of plunger movement. When it is not, movement of thearm will be restricted by this pin and the readings will be inaccurate.

Accordingly, one of the prime objects of my invention is to design aninside attachment for a test indicator of the type herein describedwhich will permit extremely accurate readings to be taken at all times,and which is highly reliable and cannot be jarred out of register.

Another object of my invention is to design an inside attachment inwhich means is provided for insuring that the full movement of theattachment arm in the axial plane of plunger movement is in no mannerrestricted, no matter in which position the means is disposed relativeto the plane of plunger movement when the attachment arm is threaded in.

A further object of the invention is to design an inside attachment andmovement confining means therefor, which permit free and full movementof the attachment in the plane of plunger movement without binding,while positively limiting all other movement which would produceinaccurate readings.

Another object of the invention is to design an inside attachment of thetype described, which is of simple and practical construction, and whichcan be very economically manufactured and assembled.

With the above and other objects in view, the present invention consistsin the combination and arrangement of parts, hereinafter more fullydescribed, illustrated in the accompanying drawing, and moreparticularly pointed States Patent 2,755,557 Patented July 24, 1956 outin the appended claims, it being understood that changes may be made inthe form, size, proportion, and minor details of construction, withoutdeparting from the spirit, or sacrificing any of the advantages of theinvention.

In the drawings:

Fig. 1 is a top plan view of a dial test indicator with the insideattachment thereon.

Fig. 2 is an enlarged, fragmentary, part sectional, elevational viewthereof, the broken lines illustrating the movement of the attachmentarm.

Fig. 3 is a still further enlarged, part sectional, fragmentary,elevational view of the attachment arm.

Referring now more particularly to the drawing in which I have shown thepreferred embodiment of my in" vention, the test indicator shown inFigs. 1 and 2 of the drawing is of the general type disclosed in PatentNo. 2,345,845. The indicator includes a base 10 with an integrallyformed extension or shank 11 formed thereon to facilitate mounting theinstrument on a tool post or the like. A passage 12 is formed in thebase in to receive a plunger 13 which is supported by a bearing 14provided on the base 10, and a removable contact head 15 is threaded onthe outer end of the plunger 13 as usual.

A cylindrical casing 16 is mounted on the base 11 to enclose the workingparts of the indicator, and a plate 17 is provided thereabove, the plate17 being secured in p0sition by means of screws (not shown) in thespacer posts 19 and 20. The plunger 13 extends through the bottom of thecasing 16 into the interior thereof, and a trans verse pin 21 is rigidlymounted in the inner end thereof, the one end of said pin engaging aworm cam 22 provided on a centrally disposed operating shaft 2.3, theopposite end extending into a vertical slot or groove 2-4 formed in thepost 20, and it will be obvious that an axial movement of the plunger 13will revolve the shaft 23, and that the plunger itself is prevented fromrotation by the disposition of the end of the pin 21 in the groove 2Depending from the plate 17 in position to be engaged by the end of theplunger 13 is a stop member 25 which limits the rotation of the shaft 23as usual, and provided within the casing 16, to normally retain theplunger 13 in its outer position, is a spring 26 secured at one end by ascrew 27 and at the other by wrapping it around one end of the pin 21.Further, a hair spring 3% is provided on the shaft 23 and is connectedto the member 25 to materially increase the sensitivity of the device.

An indicator hand 28, having a central hub 29, is nonrotatably mountedon the outer end of the shaft 23, and a dial 31, which is usuallygraduated in thousandths of an inch, is provided thereunder, it beingobvious that the worm cam 22 is so pitched that the exact linealmovement of the plunger 13 is accurately represented on the dial .31.

The dial 31 is mounted in a new and improved bezel unit which can berapidly and easily assembled and disassembled, and which forms thesubject matter of a copending application for Dial Test Indicator,Serial No. 331,890, filed January 19, 1953, by Charles Zelnick, nowPatent No. 2,726,626, issued December 31, 1955, and will not be hereinfurther described. Broadly, a given number of circumferentially spaced,horizontal slots 32 are formed in the wall of the casing, and mountedwithin the casing and bearing against the inner face of the side wallthereof, is a split annular spring 33 which is formed with apredetermined number of circumferentially spaced, offset portions 34 toproject through the slots 32.

A lower bezel member 36 is adapted to be slipped over the upper portionof the casing 16 previous to insertion of the spring 33, the member 36being formed with a lower flange 37 to space the bezel member 36 fromthe Wall of the casing 16, all as clearly shown in Fig. 2 of thedrawing, and it will be apparent that when the spring 33 is inserted,the offset portion 34 of the spring will engage the inner peripheralwall of the member 36 and resist rotative movement thereof, so that themember 36 can be set in a given position with relation to the indicatorhand 28. Since the flange 37 is disposed directly below the offsetportions 34 of the spring 33, the bezel member 36 is also prevented fromslipping oi? the casing 16. An intermediate interior flange 37 formed onthe bezel member 36 to rest on the upper edge of the casing 16, and thegraduated dial 31 is mounted on said flange in frictional engagementwith a shouldered portion 38 of the bezel member 36, so that the dial 31revolves with the member 36.

A transparent crystal 39 is suported above the indicator hands 28 by aspacer ring 40 to close oti the indicator chamber and prevent dirt anddust from entering the device, and an upper bezel member 41 is adaptedto snap over the shouldered portion 38 to retain the crystal inposition. Thus, it will be obvious that the entire bezel assemblyrevolves as a unit, the upper bezel member 41 frictionally engaging theshouldered portion 38 of the lower bezel member 36.

The inside attachment A which forms the subject matter of the instantinvention comprises a support 42 and an attachment arm 43 swivellymounted in a socket 44 formed in the outer end of the support 42. Thebase of the test indicator is bored as at 45 to accommodate the innerend of the arm 43, and the outer end of the bore 45 is interiorlythreaded as at 46 so that the threaded support 42 may be screwedtherein.

The attachment arm 43 is enlarged intermediate its ends to form a balljoint 47 which seats in the socket 44, and it will be ovious that theattachment arm 43 pivots in the socket 44 when its outer end is moved,and that the inner ball end 48 thereof, which seats in the socket 49 inthe plunger 13, moves the plunger 13 to register the reading inaccordance with the degree of movement. To limit the swivelling of thearm 43 and prevent its turning or revolving in the socket 44 about itsaxis, a slot 50 is provided in the ball joint 47, and a transverselydisposed pin 51 is mounted in said support and extends into said slot.The pin 51 is a sufiiciently close fit in the slot 50 to preventrevolution of the arm 43 without binding the arm 43, and I wish todirect particular attention to the fact that the pin 51 need not bedisposed in the axial plane of plunger movement of the device to operateaccurately. If it is, the ball joint 47, of course, moves back and forthguided by the pin 51 which prevents its revolving sideways in the ballsocket. If the pin 51 is disposed at right angles or with respect to theplane of plunger movement, the ball joint 47 still moves in that planeand the action is one of fulcruming on the pin 51. In the event that thepin 51 is disposed at a 45 angle with respect to the axial plane ofplunger movement after the attachment arm has ben screwed in, the armstill moves in the same plane, half of the motion occurring as the balljoint guides on the pin and half as it fulcrums on the pin 51. By thesame token, if the pin is disposed at other points between the aboveposition, the motion will occur in a ratio of, for example, 63 offulcruming movement on the pin to 37 guiding movement, or the like.

From the foregoing, it will be obvious that I have perfected a verynovel and improved inside attachment for dial test indicators which isextremely accurate no matter how far it is screwed into the indicatorbase, and which can be economically manufactured and assembled.

What I claim is:

l. A dial test indicator including a casing having a removable, workengaging, inside attachment received by the casing comprising, a plungerslidably mounted in said casing, indicating means operably connected tosaid plunger and actuated into indicating position by axial movementthereof, said attachment comprising an elongated barrel which isreceived by the casing and an attachment arm having an enlarged balljoint intermediate its ends extending through said barrel, an end ofsaid arm being in said casing and being operably associated with theplunger to transmit movement of the opposite end thereto, and the barrelhaving a socket formed therein to swivelly receive said ball joint, thesaid opposite end of the arm being unobstructed so that it can engage awork surface, and means in said barrel in engagement with the ball jointpermitting unrestricted pivoting of said joint in the axial plane ofmovement of said plunger to record a true measurement regardless of theangular disposition of the means relative to the axial plane of movementof the plunger, caused by said casing receiving the barrel in differentcircumferential position when the attachment is replaced after removal,while preventing revolution of the ball joint in said barrel about theaxis of the arm.

2. A dial test indicator including a casing with a threaded openinghaving a removable, work engaging, inside attachment threaded into saidopening comprising, a casing including a graduated dial, a pointer forsaid dial, a plunger reciprocable in said casing extending transverselyrelative to said opening, means connected between said plunger andpointer to translate axial movement of said plunger into rotation ofsaid pointer to cause the latter to indicate relative to said dial, saidattachment comprising an elongated barrel with a threaded end receivedin said opening and a straight attachment arm having ball members oneach end and an enlarged ball joint intermediate its ends, the plungerhaving a socket receiving the ball on one end of the arm and the barrelhaving a socket swivelly receiving the intermediate ball joint, theopposite end of said arm extending outwardly beyond said barrel andbeing unobstructed so that it can engage a work surface, said ball jointhaving a groove parallel to the axis of the arm, and a pin fixed in saidbarrel perpendicularly to the said axis of the barrel projecting intosaid groove and permitting unrestricted pivoting of said joint out ofthe axis of the barrel in the axial plane of movement of said plunger torecord a true measurement regardless of the disposition of the pin at anangle to the plane of plunger movement, while preventing rotation of theball joint in the barrel about the axis of the arm.

3. A dial test indicator including a casing having a removable workengaging, inside attachment received by the casing comprising,indicating means in said casing including a member having movement in acertain general plane and an indicating member, said latter member beingactuated to an indicating position from another position by movement ofsaid other member in said plane, said attachment comprising an elongatedbarrel which is received by the casing and an attachment arm having anenlarged swivel joint portion intermediate its ends extending throughsaid barrel, an end of said arm being in said casing and being operablyassociated with the indicating means to transmit movement of theopposite end thereto, and the barrel having means swivelly receiving thesaid joint, the said opposite end of the arm being unobstructed so thatit can engage a work surface, one of said arm joint and barrel having agroove parallel to the axis of the arm, and the other having pin meansprojecting into the said groove and permitting unrestricted pivoting ofsaid joint in the plane of movement of said first mentioned member ofthe indicating means while preventing axial revolution of the attachmentarm in said barrel.

References Cited in the file of this patent UNITED STATES PATENTS2,026,444 Trott Dec. 31, 1935 2,345,845 Wells Apr. 4, 1944 2,401,838Mitchell June 11, 1946

